The present invention generally relates to packaging and more particularly to a method and apparatus for making unitary packages which hold a plurality of components, each package containing a load wrapped in a web of stretched netting material.
Case packing or boxing is a common way of shipping multiple unit products. The multiple unit produces are generally stacked in a corrugated box or are wrapped with kraft paper with the ends of the kraft paper being glued or taped. Another way of shipping such products is by putting a sleeve or covering of heat shrinkable film around the products and shrinking it to form a unitized package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798; 3,626,654; 3,590,509 and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
The present invention provides a simple, reliable and inexpensive method of unitizing multiple unit products into a single wrapped package with an overwrap material which cannot take a heat seal.
When the present process and apparatus is compared with other apparatus and processes currently used to pack products in corrugated boxes and the cost of the corrugated boxes themselves, the invention shows an enormous cost savings. The invention has comparable costs with kraft wrap but it gives a much tighter and better unitized package than that possible with kraft wrap. In addition to these factors the invention can use a stretch netting material, stretch mesh material or perforated stretch film which provides product visibility not possible with kraft or corrugated wrapping plus the desirable feature of letting the load "breathe." This feature is especially desirable when live produce is packaged and shipped. Furthermore, the present invention system offers packaging speed, reliability of package seal and energy savings in that less energy is required to package the products.
A basic problem with shrink and non-cling stretch film packaging is that the primary strength and reliability of the package is determined by the consistent quality of the seal. These seals depend on a careful maintenance of the sealing jaw and are never as strong as the film itself. The time that it takes to make the seals is a limiting factor on the possible speeds of most shrink systems with the additional problem that some stretchable materials, as for example stretch netting, cannot be heat sealed.
The present invention does not require a structural seal and therefore can use any type of stretchable material. The invention is designed to function with a stretchable plastic netting material such as that known in the trade as "stretch net" manufactured by Bemis Bag but can be used with other stretchable film webs such as P.V.C. or polyethylene. In the present invention the apparatus utilizes a tucking mechanism which effectively tucks a wrapping of film under the wrap adjacent it while severing the trailing edge of the film from the load after the load has been spirally wrapped.
The use of spiral wrapping machinery is well known in the art. One such apparatus is shown by U.S. Pat. No. 3,863,425 in which film is guided from a roll and wrapped around a cylindrical load in a spiral configuration. A carriage drives the film roll adjacent the surface of the load to deposit an overlapping spiral wrap around the load and returns in the opposite direction to deposit another spiral overwrap around the load. Other spiral wrapping apparatus are described by U.S. Pat. Nos. 3,857,486; 3,788,199; 3,549,017; 3,412,524, 3,191,289 and 2,716,315. The previously indicated patents rely on heat shrink material, adhesives, a heat seal or the tacky nature of the film to hold the outer layer of wrap in a fixed position.
The turntable clamping assembly described in this specification is disclosed in U.S. Pat. No. 4,077,179. Various patents have described the use of mechanisms for wrapping materials. In U.S. Pat. No. 3,003,297 a complex cutting and holding mechanism is used to place tape on a box and cut if off with the process being repeated for each box. The use of adhesive on the tape to bond it to the package is an integral part of the function of this concept. Without this adhesion it would not work either in single, multiple or spiral configurations. The unique design and function of the tucking, clamping and cutting mechanisms in the present invention does not require a bonding or heating of the film in order for the system to operate.
U.S. Pat. No. 2,088,133 discloses a reverse wrapping wire tying machine. In the reference a gripper mechanism holds a band in position with respect to the load to be wrapped and a rotatable ring drive rotates the band around the load until the band has completed more than one wrap of the load and passes over the body of the gripper mechanism. A separator slide is used to separate the leading edge of the band from the underlying band and a second gripper mechanism attaches to the separated band. A heat sealing mechanism welds the wrapped layer band to the band underneath it and a cutting mechanism severs the leading edge of the band held by the second gripper mechanism which then becomes the trailing edge of the succeeding wrap. When the band is severed the ring drive mechanism is rotated in a reverse direction for the following load with the various gripping and cutting mechanisms functioning in the same manner.
Additional references of interest which are pertinent to rotatable drives for wrapping packages are disclosed in U.S. Pat. Nos. 3,820,451, 3,331,312, 3,324,789, 3,309,839, 3,207,060, 2,743,562, 2,630,751, 2,330,629, 2,054,063 and 2,124,770.
Other applications in packaging are shown by U.S. Pat. Nos. 3,514,920 and 3,793,798 in which heat shrink film is wrapped around a pallet supporting a plurality of cartons. A similar full web apparatus using a tensioned cling film is shown by U.S. Pat. No. 3,986,611 while another apparatus using a tacky P.V.C. film is disclosed in U.S. Pat. No. 3,795,086.
The present invention uses stretchable plastic netting in its preferred embodiment since the mechanical stretching of the netting utilizes its strength better than heat shrink wrap and can be used on loads where breathing is necessary or no heat can be applied to the product. The elasticity of the netting or film holds the products under more tension than either the shrink wrap or the kraft wrap particularly with products which settle or relax when packaged.
Various apparatus and processes have been developed by the named inventors of this invention to utilize stretch material in package wrapping. Such apparatus and processes are disclosed in U.S. Pat. Nos. 3,867,806, 4,050,220, 4,077,179 and 4,079,565.
Additional benefits occur in the present invention over the prior art in that no changeover is required in handling random size units of a variety of materials as the apparatus is constructed to handle such random size units. Furthermore, the apparatus provides a substantially continuous wrapping operation so that loads can be wrapped at any desired speed and for any time period. A significant economic factor is also present in the present invention as the power requirements are significantly less than those of shrink systems since there is no heat tunnel required and greater speeds of operation are possible because of the elimination of the conventional heat seal which is used in non cling wrapping. Furthermore a wider number of products can be handled by the present invention because of the elimination of the heat seal requirement. It should also be noted that adhesives do not work efficiently on the netting material due to the lack of gripping surface. Because of the simplicity of the construction of the invention there is a greater stability in the inventive wrapping apparatus with less maintenance being required to maintain the apparatus resulting in a corresponding reduction in breakdown time. Another desired characteristic resulting from the apparatus construction is that the invention does not take up much floor space.